Portable drafting machine



y 1954 G. c. LUEBKEMAN 2,682,708

PORTABLE DRAFTING MACHINE Filed May 3, 1952 INVENTOR.

. E Gem-ye C. Luefemarz WM xi"? Patented July 6, 1954 PORTABLE DRAFTINGMACHINE George C. Luebkeman, Cincinnati, Ohio Application May 3, 1952,Serial No. 285,879

9 Claims.

This invention relates to drafting machines and has for an object theprovision of a primarily portable device which can be convenientlycarried in the coat pocket or in the briefcase and which is primarilyadapted for comfortable and accurate use and ambulatory adjustment withone hand without necessitating the employment of fastening means on thedrawing surface.

Another object of the invention is to provide a simple, reliable andrelatively inexpensive device for the stated purposes which deviceaffords to the user an exceptionally easy and rapid adjustment to therequirements in making or check- 7 ing a drawing of any size.

A further object of the invention is to provide a machine of thischaracter which is provided with means adapting it to use inenvironments other than on a drawing board without loss of itsadvantages of easy and extremely flexible ambulatory and swingingadjustments.

These and other important objects, hereinafter made apparent, areattained by the means described herein and exemplified in theaccompanying drawings, in which:

Fig. 1 is a perspective view of a pocket drafting machine embodying theinvention operatively held by the users hand.

Fig. 2 is a top plan view of the device, partly broken away.

Fig. 3 is a cross sectional view taken on line 33 of Fig. 2. s

Fig. 4 is a cross sectional view taken on line 4-4 of Fig. 2.

Fig. 5 is a cross sectional view taken on line 5--5 of Fig. 2. V

Fig. 6 is a cross sectional view taken on line .65 Of Fig. 2.

Fig. 7 is a cross sectional view showing a means for securing themachine to a small portable drawing board.

It is known in the art to employ a jointed parallel arm assembly havingat its opposite ends a drafting square and a base or another draftinginstrument, the base forming portion being either permanently ortemporarily secured to the drawing board in use.

It is the particular object of the invention to provide a draftingmachine that is primarily adapted for convenient and accurate usewithout the necessity of employing any securing means, but isnevertheless capable of exceptionally easy adjustment which affords theoperator a reliable, comfortable and very flexible control of themachine in its desired relation to any portion of a drawing surface. Themanipulation is under practically all circumstances controlled by onehand of the user while the users other hand is free to execute thedrawing or checking of lines with a pencil or comparable instrument.

In its preferred form the drafting machine employs as a base or normallystationary memher a protractor 8, which may be of transparent plasticmaterial, having a true diameter line 9 thereon which is parallel to astraight edge In of the protractor. At the true radial center of theprotractor 8 there is provided a finger piece II with a reducedcylindrical stem [2 which may turn freely and reciprocate slightly in abore l3 that is centered exactly at the true radial center of theprotractor. Counterbores I4 and 15 are provided in the top and. bottomfaces of the protractor to selectively receive the upper and lowerdisc-like enlargements I6 and I1 respectively on the ends of stem l2which spaces said enlargements from each other at a distance sufficientto allow the enlargement I! to shift into or slightly out of counterboreI5 and selectively engage the antiskid surface l8 of enlargement I! on adrawing surface when digital pressure is applied on top of piece H andto thus permit the protractor 8 to be adjusted about its true radialcenter. The finger piece II also has an axial bore [9 to admit a pencilpoint or a push pin for marking or for temporarily holding the trueradial center on the drawing if desired when the drawing and the deviceare left idle. The

vbase or protractor 8 also has bores 20-20 adjacent opposite ends of thetrue diameter line 9 for marking or securing purposes if desired. Asuitable clamp such as 2| may be employed having a slender lug 22 forentry into one of the bores [9 or 20 for temporarily fixing the machineon a small drawing board 23 if such a combination is wanted.

The semicircular margin of protractor 8 is suitably graduated as at 24through one hundred eighty degrees on one side of diameter line 9 and isprovided in known manner with reversely readable indicia 25 and 26.

The important feature of the present drafting machine of the inventionis its combination of simple means which afford an improvedmaneuverability of the machine in a stepwise ambulatory fashion oversuccessive areas of a drawing surface and the relative adjustment of itsmembers on opposite ends of the jointed arm assembly 21 to carry on thedrafting or checking operaticns without the use of fastening means. AnL-square indicated generally at 2B or any other drawing implement ispivotally connected at one end of the arm assembly 27, which assembly ispivoted at its opposite end to the base or protractor member 8.

As shown in the drawings, assembly 21 comprises an annular joint member29 which has .the ends of a pair of parallel links 3D-3| pivoted on itstop at diametrically opposite sides thereof .by means of rivets at 32and 33. The links 30 and 3| have their remaining ends pivoted on top ofthe L-square on rivets 34 and 35 that are located on the longitudinalcenter of the drawing scale 36 which may be an integral or a removablepart of said'L-square 28. An upstanding finger knob 3.1 is mountedbetween. the pivots 34 and 35 and relatively closer to the pivot 34 sothat the stem of the knob 31 serves as a stop for arm to limit thepivotal movement of L-square-28- in one direction about its pivots 34and 35. A

stop pin 38 (or in lieu thereof another knobsimilar to 31) locatedrelatively. elose-tothe pivot.

35, limits pivotal movement of arm 3| in the opposite direction. Thelinks 3ll'and 31. cannot approach each other closely enough toimpair theaccuracy of their parallel relation.

The remaining links 39 and 40 respectively have ends pivoted on rivets4| and 42 to the lower face of joint member 23 atdametrically oppositesides. thereof. I preferably dimple the-member 29 to provide shallowdished places inits top face to receive the heads of the pivot formingrivets 4! and 42' in substantially countersunkrelation with the topface. of. member 29. The member 2'9'has the. heads of rivets 32' and 33substantially countersunk in shallow dished places in the bottom face ofsaid member 29. This arrangement affords a sturdy mounting. and.interference free operation of the pivoted links on the annular jointmember 29.

The remaining ends of links 39' and 40: are pivotally connected to thetop face of the protractor or base member 8 by means of rivets 43 and44. The L.-square 28' is thusshiftable relative to the straight edge IUof the protractor with the scale arm 36 in parallel relation in knownmanner of'operation of a drafting machine;

In order to enable the, user. to holdthe pro.- tra-ctor 8' innon-shifting. relation at a selected place on the drawing with one handand also permit the same hand to manipulate the L-square 28 throughoutan area of the drawing sheet adjacent the protractor I have provided'onthe bottom face of 'the. protractor. or base 8; sufficient antiskidsurface.45.to,enab1e saidbase to beheld in position. on the drawingwhile the weight oil the users-left-hand rests the-top ofthe said base.For this purpose several patches-or areas 45 of "antiskid surfacing maybe used. and may be formed of dried rubber cement. film. or, fine gritabrasive. suitably fixed. on the base.

A.- slightly cupped hand rest indicatedgenera-lly at. 46 is mountedv forrotation on. top. of base-8 and in parallelism. with the latter. Thehand rest 46 comprises an upper disc portion. which overhangs aconsiderable areaof the base 8 and is dished or cupped at 48. in. theupper center thereof so that the heel or outer bottom carpal portion 49of a users hand 50 may comfortably and non-shiftably rest thereon whilepermitting the hand toswivel with its supporting rest relative to thebase 8 while. the latter is held against sliding or turning on thedrawing under the weight of the hand 50 on said hand rest. The disc 41has an integral hub 5| on the bottom and is rotatably held in slightlyspaced relation by a center pin or rivet 52, A simple ball race 53 isinterposed between base 8 and disc 4! and it turns freely about thecircumference of hub 5|. Bea-ring balls 54-disposed in individual holesin theball race 53 afford a free turning and steady support for the discas the hub and disc may turn on the ball bearing support with aminimumof wear. on the center pin 52. Disc 4'! may be of a diametersufficient to overhang the finger piece II by peripherally cutting ornotching the disc as at 55. The notch can be brought into registry withthe top of the finger piece to render the latter accessible whendesired.

It istobe: observed thatithe outer circumference of the race member 53serves as a limit stop for either the link 39 or the link 48 when saidlinks are turned on their pivots 43 and 45. The links-39-and40 are thusalso prevented from so closely approaching each other in their movementsas to impair the parallel positioning.

The holdingof the protractor 8 with its straight edge l0..on a givenline will be readily understood'since either the heel of the hand or oneor more fingers of the hand 50 may comfortably rest in the cupped center48 of the hand rest 46 while the index finger ofthe same-hand may seatin the cupped top 56-of-the finger knob 3-? on the L-square 28. Theindex finger may be extended or retracted to'shift the L-square relativeto the protractor and that part ofv the hand which rests on member mayturn and swing as the hand rest 46-rotates on itsbearing support withoutrelaxingthecomfortable resting of the weightof the handon said supportand without danger of accidental shifting of the protractor base 8 onthe-drawingsurface. The ability of different users 'witheitherlarge or,small hands to quickly adapt themselves to an individually comfortable,rapid and easy mode of operation is to be noted. It'willbe-understood.the usualoperations'of shifting the L-sq-uare to successive positionsin'the fieldofadjustment of-the L-square about theprotractor; base 8"may be advantageously performed: by the same hand which rests on" member46 and: thus holds the protractor against shifting on' the drawing. Whenlines are to bedrawn the l.--square is heldfirmly by digital. pressureon knob 31 while the position of the base-8 ismaintained bytheweight ofthe users'hand on member 461 In order that. the digital;holding of, theL- square- 28*and the" shifting of said" square rela tive to theprotractor may be suited'to the greatest ease andcomfort'for the banditof 'theuser I prefer to. providethedrawing scale members 36 and 36l' ofthe' l.'-square and also the link 3.3 with tappedbores 310 located atsuitable distances away from' the finger knob 37 and one or moreoptionally. employed finger knobs 310i) are provided for selectivemounting in one or more of. said bores, Inthisway thedisposition of'thefinger knobor knobs may be accommodated to facile operation by almostany person regardless of thesize or of the normal or handicappedcondition of, the. hand. to be used for controllingv the machine. Theselectively employedifinger knobsf31'00i are desirably lower than thefinger knob 31 but all of said knobs have concaved tops toafford easydigital control of the machine and. a. maximum. comfortable support for.the, entire hand.

A. person. whose hand is supple and. whose fingers are. relativelynimble. can hold the L- square in an adiusteolzposition and'then lightlyshift the base 8. to another place for drawing in another area. bymanipulation v Withone hand only. The user may. conveniently turn thehand rest to bring. notch 55. in registry. above finger piece ll andthen placedigital pressure on the latter and thereafter adjust theprotractor about its radial center. Ordinarily. the right. hand or thepencil. in. thesright hand-is employed. in assisting in the lastmentioned two operations since the act of drawing is momentarilyinterrupted.

One who draws with the left hand can manipulate the machine asillustrated with his right hand by disposing straight edge it on theperpendicular instead of horizontal. Obviously the machines can be madefor left-handed persons by pivoting links 39 and 40 on the left-handside of the protractor 8 instead of on the righthand side as hereinillustrated.

For adapting the instrument to use on a drawing supported by or scribedon a ferrous metal surface I have provided permanent magnets 5! embeddedclose to the bottom surface of protractor 8 to materially assist inmaintaining the position of the latter. The device is thus madeavailable for use in making original layouts on sheet metal and flatsurfaces of castings and in checking the same.

The parts other than the jointed parallel arm assembly are desirablymade of transparent plastic materials from which they can beinexpensively formed into light weight drafting machines that can beeasily carried about in the monly found on drafting boards, and if atemporary slidable attachment is desired, the holes 20-29 may receiveholding lugs on any suitable friction slide to connect said base withthe parallel straight edge device carried by the drafting board.

It is to be observed that by moving the links 39 and 40 about theirpivots until arm 39 engages the ball race 53 as a stop, the joint member39 will assume a position below the straight edge l0 and close to theprotractor. The arm assembly can then be jack knifed to a foldedposition with the L-square superposed over the protractor. When thusfolded the device occupies a minimum of space and is storable in thebriefcase or the pocket without liklihood of accidental damage.

The machine of the invention will be understood to be subject tomodification within the spirit of the invention and the scope of theappended claims.

What is claimed is:

1. In a portable drafting machine the combination with a flexible unitcomprising a drafting instrument and a jointed parallel arm assemblyhaving said instrument pivotally connected to one end thereof, of a basepivotally connected to the other end of said arm assembly, an antiskidbottom on said base, a hand rest connected to the top of the base forrelative swivel movement in parallelism with the top of said base, and afinger knob mounted on said flexible unit.

2. In a portable drafting machine the combination of a base having anantiskid bottom, a swiveled hand rest connected to the top of the base,a jointed parallel arm assembly pivoted at one end on top of the base, afinger piece extending through the base and adapted for relativerotation and limited axial reciprocation therein, said finger piecehaving an antiskid bottom end, a jointed parallel arm assembly pivotedat one end on the top of said base, a drafting instrument pivotallyconnected to the opposite end of said arm assembly and a finger knobselectively connected to said arm assembly and said instrument.

3. A portable drafting machine comprising a protractor having anantiskid bottom face, a hand rest swiveled at its center on top of saidprotractor, a parallel arm assembly including a joint member and twopairs of links each having an end pivotally connected thereto in knownmanner, a drafting instrument having the remaining ends of one pair oflinks pivotally connected thereto, the remaining ends of the other pairof said links being pivoted to the top of the protractor, and a fingerknob on the drafting instrument.

4. In a device of the class described a protractor having an antiskidbottom face, a hand rest swiveled at its center on top of theprotractor,

a drawing instrument, and a parallel arm as-.

sembly connected at its opposite ends on top of said protractor and saidinstrument respectively.

5. The combination as set forth in claim 4 characterized by theprovision of a rotatable finger piece extending through the protractorat the true radial center thereof, said finger piece having an antiskidbottom end adapted to assume a selected position at and slightly belowthe bottom face of the protractor.

6. The combination as set forth in claim 4 characterized by theprovision of a finger piece adapted for rotation and slightreciprocation in the protractor at the true radial center thereof, andby the provision of a notch in the edge of the hand rest adapted forradial alignment with the top of the finger piece and affording digitalaccess to the top of the latter.

7. The combination as set forth in claim 4 characterized by theprovision of a finger knob selectively mounted on top of the drawinginstrument and arm assembly to permit one part of a users hand to besupported on the hand rest for swiveled movement therewith relative tothe protractor for retaining the latter against shifting on a supportsurface, while a finger of the same hand controls and selectively shiftsthe drawing instrument relative to the protractor.

8. The combination as set forth in claim 4 characterized by theprovision of permanent magnets embedded in the bottom of the protractor.

9. In a portable drafting machine, a base having an antiskid bottomsurface, a swiveled hand rest on top of the base, a jointed parallel armassembly comprising a first pair of parallel links pivoted at one end atrelatively opposite sides of the swivel mounting of the hand rest on topof the base whereby the said mounting serves as a stop limiting pivotalmovement of the respective links on the protractor, a second pair ofparallel links comprising said arm assembly being pivoted in spacedrelation on the drawing instrument, and means on said instrumentlimiting pivotal movement of said second pair of parallel links.

References Cited in the file of this patent UNITED STATES PATENTS Number

